The devices or jigs that are in current use are formed by two frames that are hinged to each other by means of two intermediate connection rods or levers that co-operate with the two frames to form a hinged quadrilateral as seen from above.
One of the frames has means for fastening it to the body of the vehicle at the door opening. The other frame has means for supporting the door itself. In certain applications, those support means include a third frame that is hinged to the second frame and that actually supports the door.
Such mounting jigs are usually made up of machine-welded structural members having manufacturing tolerances that are large in order to keep cost price down. In particular, the pivots via which the frames are hinged together are of the door hinge type with hinge pins that co-operate with eyelets in hinge plates or straps. The accuracy with which such hinge portions are assembled by welding requires a considerable amount of slack to be arranged between the pin and the eyelet, that slack degrading the accuracy of the relative positioning of the frames and thus the accuracy of the relative positioning of the door panel and of the body. Unfortunately, such positioning needs to be accurate, at least when the frames are brought one against the other and the door is in the vicinity of its opening. In addition, that large amount of slack leaves a gap that fills with the substance with which the body is being treated (paint, stripper, etc.), which can lead to the pivots rapidly becoming clogged such that provision must be made for frequent cleaning, that requiring considerable action to be taken on the equipment.
In order to remedy those drawbacks, proposals have been made (see FR 2 854 862) for a vehicle door mounting jig that comprises a first frame having means for adjustably fastening it to a vehicle body in the vicinity of the door opening, a second frame having means for supporting the door of the vehicle on said second frame, and connection arms for connecting the first frame to the second frame, which arms are hinged to the first frame and to the second frame so as to cooperate with those frames to form a deformable quadrilateral in which the hinges between the arms and the frames are ball joints.
That configuration is entirely satisfactory in production, in particular since it has been the subject of an improvement described in FR 2 937 611 that makes it possible to calibrate each jig properly in a few minutes, i.e. to obtain rapidly the positions of the various ball joints so that the door panel is placed correctly relative to the body, mainly when the panel is brought into the vicinity of the door opening.
It has been found that it is not easy for an operator to maneuver the frame carrying the door relative to its support that is fastened to the vehicle, in particular because the painted door cannot be touched or because the operator is in an awkward position relative to the body, or because the body is immersed in a cataphoresis bath, etc.